The Problem

Posterior glenohumeral instability represents approximately 2-12% of all patients with pathologic shoulder instability. The underlying pathology classically involves a posterior labral tear and/or laxity of the posterior capsule. Clinically, this is manifested as a spectrum from a rare traumatic posterior glenohumeral dislocation to more common recurrent posterior subluxation in an athlete due to repetitive stress in the provocative position of shoulder flexion, adduction, and internal rotation. A detailed history and focused physical exam is required to make the diagnosis and guide treatment of this increasingly recognized cause of shoulder symptoms and disability.

Clinical Presentation

A 19-year old collegiate football offensive lineman presents with complaints of vague posterior shoulder pain. Symptoms are exacerbated when blocking an oncoming defensive player or when performing push-ups with his shoulder flexed, adducted, and internally rotated. He feels that his shoulder is “loose” when engaged in blocking another player. The patient states that he recalls a remote episode consistent with a subluxation event, but he denies any frank dislocation. He denies any symptoms at rest.

Diagnostic Workup

Provocative maneuvers aimed at assessing posterior instability include the load and shift test, the Jerk Test, and the Kim Test. The load and shift test is performed with the patient supine and the arm abducted and forward flexed 45-60 degrees in neutral rotation. A posterior and axial force is applied and the shoulder is graded for translation relative to the glenoid rim. The Jerk Test is performed by placing the arm in 90 degrees of abduction and internal rotation with the elbow flexed. An axial force is then applied to the humerus and the arm is adducted to a forward flexed position. A “clunk” is positive for posterior subluxation. The Kim Test is performed with the patient seated and the arm in 90 degrees of abduction. The arm is then flexed to 45 degrees of forward flexion while applying an axial and posterior-inferior force on the humerus. Pain associated with this maneuver is considered a positive test, and when combined with a positive Jerk Test is 97% sensitive for a posterior labral tear. In our experience, an anterior apprehension test is occasionally positive in these patients, but typically reproduces posterior pain.

Plain radiographs are useful to assess for a reverse Hill—Sachs lesion on the anterior humeral head on the axillary or Stryker notch view. A West Point axillary view is useful for assessing the glenoid and detecting osseous defects of the posterior glenoid rim. In the setting of osseous defects, a CT scan with 3D reconstructions can provide size and morphology details. MRI is the most useful imaging modality for assessing the posterior capsulolabral complex (Figure 1 and Figure 2). MR arthrogram is helpful for assessing the labrum but not considered necessary in all cases with current MR technology.

Figure 1.

Posterior labral detachment as seen on a non-contrast axial MR image.

Figure 2.

Posterior labral detachment as seen on a non-contrast sagittal MR image.

Non–Operative Management

Initial management is focused on a course of physical therapy targeting the dynamic stabilizers of the shoulder (rotator cuff and periscapular muscles) to compensate for the deficient static structures. Avoidance of aggravating activities is also recommended during the treatment phase. Non-operative management could be continued for 3-6 months prior to considering operative intervention as long as the patient is not experiencing frequent and persistent instability events.

Indications for Surgery

When considering surgical management for a patient with posterior glenohumeral instability, one must ensure the physical exam findings and symptoms are correlated with the imaging findings. Patients with recurrent frank posterior dislocations are candidates for operative management. Patients with recurrent posterior subluxation and instability symptoms that have failed a reasonable course of non-operative management are also indicated for surgical treatment.

Surgical Technique

Equipment needed:

basic arthroscopy tray

4 mm 30 degree arthroscope

7 mm canula or larger diameter,

arthroscopic mechanical shaver +/- burr

liberator or tissue elevator instrument

suture-passing device such as bird-beak or suture lasso

fixation device of choice

The procedure can be safe and effective in both beach chair and lateral decubitus positioning. It is our preference to position patients, particularly when addressing labral pathology, in the lateral decubitus position due to easier access to the inferior glenoid and potential lower risk of axillary nerve injury. A beanbag is utilized with an Acufex shoulder traction tower and typically 10lbs of traction. The shoulder positioning is 45 degrees of abduction and 20 degrees of forward flexion. After a thorough examination under anesthesia to assess directional laxity, a standard posterior portal is established and a diagnostic examination is performed to assess cartilage disease, labral integrity, and tissue quality as well as capsular volume (drive-through sign). An anterosuperior portal is established from outside-in utilizing a spinal needle, and a standard canula is placed. Any debridement/probing that is accessible from the anterior portal is performed at this point followed by switching portals with a switching stick technique.

Viewing from the anterior portal, a single posterior portal can be utilized (8 mm canula) for the repair as long as it is in proper position. Alternatively, a low or accessory posterolateral portal can be established with spinal needle guidance to access the more posteroinferior glenoid (Figure 3 and Figure 4). At this point, typical labral repair preparation is performed (Figure 5). This includes elevation of the labrum, debridement of fibrous tissue, and obtaining a bleeding bony bed (burr/rasp). Anchors can be placed through the canula or percutaneously at the glenoid edge and sutures passed through the tissue with a suture lasso device. Alternatively, if using a single portal repair technique, an angled birdbeak can be utilized. Typically three to four anchors are placed for adequate fixation (Figure 6 and Figure 7). We currently prefer to use small biocomposite anchors and tie the sutures to best control tension. We also feel that restoring labral height is important in glenoid labral repair and make attempts to create a robust labral bumper.

Figure 3.

Spinal needle localization of posterolateral portal.

Figure 4.

Canula placement for posterolateral portal.

Figure 5.

Glenoid preparation.

Figure 6.

Suture anchor repair of posterior labrum.

Figure 7.

Suture anchor repair of posterior labrum.

If capsular laxity is recognized, incorporating the capsular tissue into the labral repair with the anchor is preferred, however utilizing a non-absorbable suture for capsular plication can also be effective (Figure 8 and Figure 9). A light debridement of the capsule with a shaver prior to plication is helpful to create bleeding and improve healing potential. Understanding the close proximity of the axillary nerve to the capsule is crucial and overaggressive capsular passes should be avoided.

Figure 8.

Posteroinferior capsular plication suture.

Figure 9.

Posteroinferior capsular plication.

Pearls and Pitfalls of Technique

Pearls

Pre-operative examination under anesthesia to assess for instability in other directions and comparison to the contralateral side

Be aware of posterior capsular laxity and incorporate distended capsular tissue into the posterior labral repair as this has been shown in our experience to drastically reduce the recurrence rate

Use of the accessory or low posterolateral portal to access the inferior-posterior glenoid (See Figure 3)

Pitfalls

Failure to recognize bony defects and excessive glenoid retroversion may result in recurrent posterior instability

One must use caution when using accessory portals such as the low or accessory posterolateral portal to avoid the posterior branch of the axillary nerve and the posterior humeral circumflex artery. A “nick and spread” technique with a small clamp is a useful way to avoid neurovascular injury.

Avoid chondral injury to the humeral head and glenoid when placing canulas and when switching between portals. The use of switching sticks allows for atraumatic camera repositioning and portal exchange. After starting in the posterior viewing portal, we then switch by driving the arthroscope/sheath into the anterior canula, removing the arthroscope, and placing a single switching stick through both portals. Then the arthroscope sheath can be placed anteriorly over the switching stick as well as the canula posteriorly. This guards against the loss of a portal, making multiple capsular incisions, and limits iatrogenic chondral injury.

Potential Complications

The most common complication encountered post-operatively is recurrent posterior instability. The posterior branch of the axillary nerve traverses in some cases within 1 mm of the inferior capsule and is at risk when passing sutures at the posterior-inferior glenoid. Over-tightening of the posterior capsule can lead to anterior subluxation and instability. Other potential complications include infection and generalized shoulder stiffness.

Post–operative Rehabilitation

The patient is initially immobilized in an abduction sling in approximately 30 degrees of abduction with the arm at the side, limiting internal rotation. Cryotherapy is utilized for edema and post-operative pain control. The sling is discontinued at 3 to 6 weeks based on the degree of capsular laxity noted. Gentle pendulum exercises as well as elbow and wrist flexion and extension exercises may be initiated immediately. Active elevation of the arm is not instituted until after the fourth week. Gentle, pain free internal rotation exercises are permitted at 6 weeks. During the 2 to 3 month period, range of motion is progressed until full passive and active motion is achieved. Eccentric rotator cuff strengthening, isotonic, and isokinetic exercises are introduced 4 to 5 months after surgery. Isokinetic strength testing is performed at 6 months and athletes can progress to sport-specific rehabilitation when they achieve 80% strength and endurance as compared to the contralateral side. Patients can return to non-contact sports at 4 to 6 months and contact sports after 6 months. Return to competitive throwing is typically attained 6 to 12 months after surgery.

(Arthroscopic capsulolabral reconstruction for recurrent posterior shoulder instability was performed in 183 athletes (200 shoulders). At a mean of 36 months postoperatively, significant improvements were noted in pain, stability, and function. Patients who underwent capsulolabral plications with suture anchors were found to have significantly greater improvement in ASES scores and a higher rate of return to play when compared to anchorless plications. Overall, 90% of patients were able to return to play, with 64% able to return to the same level postoperatively.)

(Level IV therapeutic case series of the operative stabilization of 136 shoulders in 131 patients with primary recurrent posterior glenohumeral instability. At a mean follow-up of 28 months, 97% of the shoulders were stable and considered a success based on the Neer-Foster scale.)

(In the position of 90 degrees of forward flexion, the primary contributor to subluxation posteriorly is the subscapularis muscle. The posterior band of the inferior glenohumeral ligament is the primary restraint to posterior translation in internal rotation and the coracohumeral ligament is an effective contributor to posterior stability in neutral rotation.)

(Arthroscopic posterior labral repair and capsular shift for traumatic unidirectional recurrent posterior subluxation of the shoulder in 27 patients. All but one patient returned to sport with little or no limitation. Significant improvements in pain score, function, ASES, Rowe, and UCLA score were noted at the time of follow up.)

(A painful jerk test was found to be a predictor of non-operative treatment failure. All patients with recurrent symptomatic posteroinferior instability and a positive jerk test were found to have a posteroinferior labral tear.)

(Prospective cohort study of 714 young asymptomatic athletes followed over a four year period for signs and symptoms of glenohumeral instability. Seven posterior glenohumeral instability events, 10% of all instability episodes, were documented. Increased glenoid retroversion was confirmed to be an independent risk factor for posterior instability.)

(A cadaveric study of various capsular plication techniques aimed to assess mode of failure, load to failure, and displacement during cyclic loading. Simple stitches were found to fail more often in the capsular tissue, whereas the mattress and figure-of-eight sutures failed at the capsulolabral junction. No significant difference was found in displacement during cyclic loading or ultimate load to failure.)

(Five cadaveric shoulders were dissected to assess the anatomy and function of the low posterolateral portal. A portal was placed 2 to 4 cm lateral and 4 to 5 cm inferior to the posterolateral corner of the acromion under direct arthroscopic visualization. The portal was a mean of 13.8 mm from the axillary nerve and 13.4 mm from the posterior humeral circumflex artery. Clinical assessment of the portal confirmed it was necessary to achieve a proper insertion angle for posterior and inferior labral anchors.)

(Therapeutic case series assessing the outcomes of a consistent arthroscopic stabilization of recurrent posterior glenohumeral instability. Thirty-four consecutive shoulders were included in the study and followed for a mean of 36 months. Significant improvement in ASES, Simple Shoulder Test, and visual analog scale scores were noted and all patients returned to their previous level of activity. Two of the 34 patients reported episodes of post-operative instability, but none required revision surgery.)

(Shah and Tung provide a comprehensive review of the mechanisms of injury and correlated MRI and CT imaging findings of posterior glenohumeral instability. Provides examples of various pathology patterns, which allows for accurate detection and management.)

Summary

Posterior labral tears are an increasingly recognized cause of shoulder disability. Accurate diagnosis requires a high index of suspicion and a systematic approach to the physical exam and use of imaging modalities. Application of the techniques and consideration of the pearls and pitfalls mentioned above will allow for safe management and consistent results for patients with tears of the posterior glenoid labrum.